The present invention relates to a light unit operating apparatus. Specifically, the present invention provides an apparatus and method for interfacing a railway signal controller with a light unit.
Colored signal light units are commonly used in railway control systems to signal the train crews as to route availability and speed requirements in the forthcoming area of railway track. Typically, incandescent light units are used as the source of light, with color added by using external colored lenses. However, non-incandescent light units, such as light emitting diode (LED) light units, are a desirable substitute as they provide a longer life, lower power consumption, and better visibility than incandescent light units. An LED light unit typically consists of a two-wire input, a power supply and a plurality of LEDs electrically connected in an array.
Electrical or electronic controllers housed in bungalows and located alongside railroad tracks may control many sets of light units, whether incandescent or LED. These controllers often employ light unit integrity tests to verify that the light unit is working, or is able to work when required. Traditionally, these controllers control and monitor incandescent light units. Traditional signal integrity testing consists of at least two separate tests performed by the controller. The first test is the cold filament test (CFT) which is applied to light units that are not currently energized. This test consists of pulses, typically less than two milliseconds in duration but repeated periodically at intervals of several seconds, which pulse the filament of the unenergized incandescent light unit. When the controller""s test signal detector senses an adequate current draw during this CFT test pulse, the controller registers that the incandescent bulb passes the CFT. If the controller does not sense an adequate current draw during the CFT test pulse, the controller registers a failed CFT. The controller also performs a hot filament test (HFT), which is applied to light units that are currently energized. The HFT provides that the light unit is periodically monitored for adequate current draw during the times that the light unit is supposed to be energized. In the event of a loss of electrical continuity between the controller and the light unit or an open filament in an incandescent light unit, both CFT and HFT tests fail.
Traditionally, when incandescent bulbs are pulsed with the CFT pulse, the slow warm-up time of the filament is such that there is no visible light output as a result of the test. However, light emitting diodes react much faster than incandescent bulbs. When this test pulsing is applied to an LED light unit it may cause a perceivable visible blink. Those familiar with the art will appreciate that this unintended blinking is an unacceptable condition.
The present invention allows quick responding non-incandescent light units to be used interchangeably with, or as replacements for, incandescent light units. The present invention also allows using the currently employed controllers utilizing the standard CFT and HFT processes, yet avoiding any undesirable blinking of the non-incandescent light units. The present invention further allows this to be accomplished without losing the ability of both the CFT and the HFT to verify electrical continuity between the controller and the light unit.
The present invention overcomes the above mentioned problems and limitations of the prior art devices by providing an apparatus and method to test the functional status of non-incandescent light units using existing controllers.
One of the preferred embodiments of the present invention includes: receiving circuitry for receiving a test signal intended for transmission to the light unit and for receiving an energizing signal; circuitry coupled to the receiving circuitry to shunt the test signal away from the light unit; circuitry for analyzing a response of the light unit to the energizing signal to determine a non-functional light unit state; and circuitry for disabling the shunting circuitry upon determination of the non-functional light unit state.
An embodiment may include the suppression of the test signal from transmission to the light unit.
The present invention provides for a signal interface module (SIM) which interfaces a quick responding non-incandescent light unit with a controller. Use of the signal interface module allows non-incandescent lights and incandescent bulbs to be driven and monitored from the same controller interchangeably, with no changes to the operation of the controller itself.
It is desired that the controllers drive and monitor non-incandescent light units while still performing both cold filament testing, and hot filament testing. Therefore, when using a non-incandescent light unit, the cold filament test pulse which otherwise could cause a visible blink of the non-incandescent light unit is shunted away from the non-incandescent light unit. A shunt completes the circuit at the SIM allowing for the detection of current flow at the controller. Thus, the present invention allows for the non-incandescent light units to be shunted during the CFT, and for no visible blinking of the non-incandescent light unit to occur, whereas if the controller is connected directly to incandescent units, the incandescent units will be subject to both cold filament tests and hot filament tests in the normal manner.
Simply shunting the light unit for the CFT would allow for the controller to continue to send CFT test pulses if the light unit has failed the HFT test. Therefore, if the non-incandescent light unit is shunted for the CFT, but no other precautions are taken, a non-functional status of the non-incandescent light unit would result in alternating status determined at the controller. The HFT would indicate light unit failure, and cause the controller to de-energize the failed light unit. The controller would then revert to CFT of the failed light unit, which may yield a xe2x80x9clight unit OKxe2x80x9d status, and allow the controller to again attempt to energize the light unit, repeating the cycle indefinitely.
An objective of this invention is to provide a consistent response to the controller in the event that the non-incandescent light unit is non-functional. When the non-incandescent light unit is functioning properly, the CFT will be shunted around the non-incandescent light unit when the light unit is de-energized, and the controller will sense an adequate current flow during the CFT. In the event that the non-incandescent light unit is not functioning properly, therefore not drawing an adequate current during the receipt of the energizing signal, the present invention employs a latch to be set, which will disable the flow of current during the CFT, causing the controller to register a failure on the next CFT. Thus, if the light unit is non-functional, the shunt of the CFT pulse is disabled and the controller will recognize a failed CFT during the next CFT therefore indicating a failed light unit under the CFT.
This application could be applied to other forms of light unit testing, such as testing of automobile traffic signals or harbor traffic signals.
An objective of this invention is to prevent the blinking effect inherent in a cold filament test of the non-incandescent light unit.
Another objective of this invention is to maintain the use of or the validity of the CFT to verify electrical continuity between the controller and a location adjacent to the light unit such as the light unit enclosure, even though the CFT is shunted around the non-incandescent light unit. This can be achieved by locating the invention adjacent to the light unit such as inside the light unit enclosure. By placing the invention near the light unit the CFT signal must travel to the adjacent location and return, therefore verifying the integrity of the electrical continuity between the controller and the adjacent location.
Another objective of the present invention is to provide for operation of the non-incandescent light unit testing over a broad range of operating voltages.
Also an objective of the invention is to provide a signal interface unit in which the signal interface unit could sense damage of its own circuitry so as to shut down in the event of damage to the circuitry.
The foregoing and other objects of the invention are intended to be illustrative of the invention and are not meant in a limiting sense. Many possible embodiments of the invention may be made and will be readily evident upon a study of the following specification and accompanying drawings comprising a part thereof. Various features and sub-combinations of the invention may be employed without reference to other features and sub-combinations. Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, an embodiment of this invention.